Panhead for camera

ABSTRACT

A camera panhead, for panning the camera about a vertical axis and tilting the camera about a horizontal axis, including fluid drag systems and a counterbalance system. The fluid drag systems each include a drag disk assembly secured to the rotating shaft and drag sector assemblies pivotally mounted to the housing and disposed about the circumference of the disk assembly to define a space containing viscous fluid. The level of drag exerted may be adjusted by pivoting the sector assemblies toward or away from the disk assembly to vary the space containing viscous fluid. The counterbalance system includes two spring sets mounted in planes perpendicular to the tilt axis. As the camera tilts, one end of each of the springs remains relatively stationary as the opposite ends rotate about the tilt axis to exert a restoring torque to counterbalance the camera. The system may be adjusted to vary the level of restoring torque exerted.

BACKGROUND

The present invention relates generally to optical equipment supportingdevices and more particularly concerns a camera panhead.

In motion and television filming, it is often necessary to sweep acamera about a horizontal or vertical axis, or both, in order to cover awide scene or follow a moving object. One of the most difficultfunctions that must be performed by a panhead is permitting the mountedcamera or other instrument to be smoothly scanned back and forth, and upand down. Both fast and slow movement must be smooth and uniform, freefrom jerking or scattering when starting or stopping. Such movement maybe difficult due to the inertia of the supported instrument and thefrictional drag inherent in the mechanical operation of the panheaditself. Achieving smooth and uniform movement may be further complicatedby other factors such as the substitution of supported instrumentshaving different weights or centers of gravity, and environmentaleffects due to the broad temperature ranges in which the panhead isrequired to function. Consequently, to provide for maximum versatilityand efficiency during usage, the panhead should provide precise movementand be light, and easily and quickly adjustable.

Various designs of fluid drag systems, such as those in U.S. Pat. Nos.2,905,421, 2,998,953, and 3,180,603, have been utilized in panheads inorder to provide smooth panning and tilting movements. While thesesystems operate effectively to provide adjustable uniform drag, manyutilize systems in which an adjustment knob may have to be turnedseveral revolutions in order to adjust the level of drag exerted by thefluid system. Such drag adjustment designs may be inappropriate forusage when an operator must quickly adjust the pan or tilt drag.

Further, a camera is often moved rapidly during use. The torque loadresulting from such rapid panning or tilting movement may cause the dragcomponents to automatically move or readjust, which results in imprecisemovement due to backlash or slop.

A counterbalancing system is often used to counterbalance the weight ofthe mounted instrument to provide a smooth tilting movement. While thetorque exerted by the tilting camera increases substantially linearly asthe panhead tilts through small angles, the torque levels off andfollows a generally sinusoidal curve as the tilt angle increases.Consequently, simple counterbalancing systems, such as linear springs,generally only operate effectively through low tilt angles. While morecomplicated counterbalancing systems, such as those using cam and rollerdevices, may operate more effectively through a wider range of tiltangles, many of these devices also do not work well at higher tiltangles.

Accordingly, it is a general aim of the invention to provide a panheadthat smoothly and uniformly pans and tilts. Another object is to providea panhead which provides precise movement with minimal backlash or slop.

A further object is to provide a panhead which effectivelycounterbalances the weight of a supported instrument by exerting arestoring torque approximately equal to the torque exerted by thetilting instrument. A related object is to provide a device whichcounterbalances the weight of the supported instrument without the useof cams and rollers. Another object is to provide a panhead which have apanning range of 360° and a full tilt range 90° from horizontal in boththe upward and downward directions.

An additional object of the invention is to provide a counterbalancingsystem which may be easily adjusted for varying weights and heights ofmounted equipment. A further object is to provide a fluid drag systemwhich may be quickly and easily adjusted to desired degrees of drag forpanning and tilting movements. A related object is to provide a panheadwhich may be locked at any desired angle, horizontally or vertically,without shifting the position of the supported instrument.

SUMMARY

The panhead includes independently adjustable pan and tilt fluid dragsystems, and an adjustable counterbalance system that exerts a restoringtorque which substantially counterbalances the torque exerted by asupported instrument. The camera or other instrument is mounted on aplatform atop a drum which rotates about a horizontal axis to providetilting movement of the camera. The drum is rotationally supported in ahousing, which is mounted for rotation on a base. The housing rotatesabout a vertical axis to provide the panning movement of the panhead.The counterbalance system contained within the tilt drum includes two ormore springs which are disposed in the planes which are perpendicular tothe horizontal tilt axis. One end of each spring is mounted at a commonaxis parallel to the horizontal tilt axis; both axes lie in a commonvertical plane. The other end of each spring is mounted at an equalangle with respect to the vertical plane. During rotation of the tiltdrum, either the commonly mounted ends of each spring or the ends ofeach spring mounted at an angle rotate about the horizontal axis, whilethe other end of each spring effectively remains stationary. As aresult, one spring shortens while the other spring lengthens as the tiltdrum rotates, such that the counterbalance spring system exerts arestoring torque which follows a generally sinusoidal curve as the tiltangle of the drum increases. Independent fluid drag systems controlrotation about the horizontal and vertical axes. Each drag systemincludes a series of linked drag sectors disposed about a drag diskassembly. The space between the drag sector assemblies and the drag diskassembly contains a viscous fluid such that, as the drag disk assemblyand drag sector assemblies rotate with respect to one another, theyexert a drag force which facilitates smooth and uniform rotation of thepanhead components.

DRAWINGS

FIG. 1 is a perspective view of a panhead constructed according to thepresent invention.

FIG. 2 is a plan view of the drag assembly adjusted for minimum dragresistance.

FIG. 3 is a plan view of the drag assembly adjusted for maximum dragresistance.

FIG. 4A is a plan view of a drag disk assembly.

FIG. 4B is a view of the drag disk assembly taken along line 4B--4B inFIG. 4A.

FIG. 5A is a plan view of a drag sector assembly partially cut away.

FIG 5B is a view of the drag sector assembly taken along line 5B--5B inFIG. 5A.

FIG. 6 is a partial sectional view taken along line 6--6 in FIG. 1.

FIG. 7 is a partial sectional view taken along line 7--7 in FIG. 6.

FIG. 8 is a partial schematic view of the counterbalance assembly asshown in FIG. 6 in a level position.

FIG. 9 is the partial schematic view of FIG. 8 rotated 90° from level inthe clockwise direction.

FIG. 10 is the partial schematic view shown in FIG. 8 rotatedapproximately 90° from level in the conunterclockwise direction.

FIG. 11 is a diagram of actual and theoretical counterbalance torquecurves for the counterbalance assembly shown in FIG. 6.

FIG. 12 is a schematic of an alternate embodiment of the counterbalanceassembly shown in FIG. 6.

FIG. 13 is a schematic of an alternate embodiment of the counterbalanceassembly shown in FIGS. 6 and 12.

FIG. 14 is a sectional view taken along line 14--14 in FIG. 1.

FIG. 15 is a partial sectional view taken along line 15--15 in FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

While the invention will be described in connection with preferredembodiments, it will be understood that I do not intend to limit theinvention to those embodiments. On the contrary, I intend to cover allalternatives, modifications, and equivalents as may be included withinthe spirit and scope of the invention as defined by the appended claims.

Turning first to FIG. 1, there is shown a perspective view of a panhead30 constructed according to the present invention. The panhead 30 isshown secured to a claw ball base 31, such as the base disclosed in U.S.Pat, No. 4,019,710, by way of a plurality platform adjustment screws 32(shown in the sectional view in FIG. 14). For mounting a camera or otherinstrument (not shown), the panhead 30 is provided with a platform 33through which extends a conventional instrument mounting screw 34. Aswill be apparent to those skilled in the art, this screw 34 threadsupwardly into a threaded hole conventionally provided in an instrumentto draw the instrument tightly and securely against the platform 33.

The panhead is defined primarily by a main body housing 35, whichsupports assemblies that control panning and tilting movements of thepanhead. The pan drag assembly 36, which includes a viscous fluid,controls rotation of the housing 35 about the vertical axis 38. Theassembly 36 is located in the lowermost portion of the housing 35. A pancover 39 is secured to the lower surface of the housing 35 to seal thefluid in the assembly 36 and prevent dirt or foreign materials frominterfering with operation of the drag assembly 36. In order to allowquick and easy adjustment of the level of drag exerted during movementabout a vertical axis, the panhead 30 is provided with an adjustmentknob 40. A numerical scale along the knob 40 permits easy identificationof level of drag for which the pan drag assembly is adjusted. Further,the panhead 30 may be locked at substantially any degree of rotationabout the vertical axis 38. In order to secure the housing 35 againstmovement relative to the base 31, a rotatable pan brake knob 42 islikewise provided adjacent the adjustment knob 40.

The platform 33 may also be rotated about a horizontal axis 42 to tilt asupported instrument up to 90° upward or downward. To permit the tiltingmovement, the platform 33 is secured to the tilt drum 44, which isjournaled for rotation with respect to the housing 35. A stationary tiltdrum cover 46 encloses the rotatable tilt drum 44 to prevent dirt orforeign materials from interfering with the tilting movement and toprovide an attractive appearance. In order to provide smooth tiltingmovement of the tilt drum 44, a tilt drag assembly 48, which includes aviscous fluid, is provided within the housing 35 at one end of the drum44. A tilt cover 49 is sealed to the housing 35 to contain the fluidwithin the housing 35 and to likewise prevent dirt and other foreignmaterials from interfering with the operation of the drag assembly 48.Quick and easy adjustment of the level of tilt drag exerted may be madeby movement of the tilt fluid adjustment lever 50. The tilt fluidadjustment lever 50 may be provided with a numerical scale (not shown),similar to the numerical scale on the pan fluid adjustment lever 40, sothat an operator may easily identify the level of drag exerted. In orderto secure the tilt drum 44 and the attached platform 33 at a desiredtilt angle, a tilt lock assembly 52 is provided in the housing 35 atopposite ends of the tilt drum 44. An operator may easily lock the tiltdrum 44 against rotation relative to the housing 35 by turning the tiltlock lever 54.

As an instrument supported on the platform 33 is tilted about thehorizontal axis 42, the instrument exerts a torque which increases asthe tilt angle increases. In order to permit uniform tilting of theinstrument, the panhead 30 is provided with a counterbalance assembly56. The counterbalance assembly 56 includes a spring system which isdisposed within the tilt drum 44 directly below the platform 33. Thecounterbalance assembly 56 exerts a restoring torque which approximatesthe torque exerted by the tilting instrument so that an operator is notrequired to work against the weight of the instrument as it tilts and sothat the instrument will remain substantially steady at a tilted anglewithout the operator supporting it. Because instruments having differentweights or centers of gravity exert different levels of torque, thepanhead 30 provides a means by which the level of restoring torque maybe adjusted to approximate the level of torque exerted by differentinstruments. To adjust the level of restoring torque, a counterbalanceadjustment knob 58 disposed directly below the tilt drum 44 may berotated. In this way, the operator may easily and quickly adjust thecounterbalance torque as well as the locking mechanisms and the level ofdrag exerted for both tilting and panning movements.

The drag assemblies 36, 48 may best be understood by referring to FIGS.2 and 3, which show the horizontal axis drag system 48. Althoughoriented differently, the vertical axis drag system 36 is constructedand operates very similarly to the horizontal axis system 48. Duringoperation, a central shaft 62 rotates with respect to the housing 35about the horizontal or vertical axis 42 or 38. The drag assembly 48includes a plurality of drag sector assemblies 64 which are pivotallymounted to the housing 35 and are disposed about the shaft 62, and adrag disk assembly 66, which is secured to the shaft 62 for rotationtherewith.

As shown in FIGS. 2 and 3, the disk assembly 66 and the sectorassemblies 64 overlap to define a space therebetween. An adjustable dragis imposed on the rotation of the shaft 62 by interposing a viscousfluid between the surfaces of the drag disk assembly 66 and thecooperating surfaces of the sector assemblies 64. The viscous substanceemployed may be any one of a wide variety, examples being oil, grease,glycerine, and the like. The frictional drag resistance created by thedrag disk assembly 66 and opposed sector assemblies 64 is directlyresponsive to the thickness of the intervening film of viscous fluid.The thinner this layer, the more resistance to relative movement betweenthe opposed surfaces results. Thus, the amount of drag resistingrotation of the shaft 62 with respect to the housing 35 may becontrolled by adjusting the space between the drag disk assembly 66 andthe sector assemblies 64. It will appreciated by one skilled in the artthat the drag assembly 48 shown in FIG. 2 is adjusted to provide maximumdrag resistance, as the space defined by the sector assemblies 64 andthe drag disk assembly 66 is at a minimum; conversely, the drag assembly48 as shown in FIG. 3 is adjusted to provide minimum drag resistance, asthis space is at a maximum.

The drag disk assembly 66 is shown in more detail in FIGS. 4A and 4B.The assembly 66 is circular with a central opening extendingtherethrough. It comprises alternating flat circular drag disks 68 andsmaller flat circular drag disk spacers 70.

As shown in FIGS. 5A and 5B, a drag sector assembly similarly includesalternating sectors 72 and sector spacers 74. Consequently, whenassembled in the drag assemblies 36, 48, the sectors 72 and disks 68will overlap, as shown in FIGS. 2 and 3. The sectors 72 will enter thespaces between the drag disks 68 as defined by the disk spacers 70, andthe drag disks 68 will enter the spaces between the sectors 72 asdefined by the sector spacers 74.

The sectors 72, sector spacers 74, drag disks 68, and drag disk spacers70 may be fabricated using a punch press die. The drag sector assembly64 may be assembled by alternately stacking the sectors 72 and thesector spacers 74, and securing the unit together with the rivets 76.The drag disk assembly 66 is likewise assembled by alternately stackingthe drag disks 68 and the drag disk spacers 70, and then securing theunit together.

In assembly of the drag systems 36, 48, the sector assemblies 64 arepivotally mounted to the housing 35 on dowel pins 78. As shown in FIGS.2 and 3, and as explained above, the drag sector assemblies 64 arepivotally mounted to the housing 35 so that the space between the dragsector assemblies 64 and the drag disk assembly 66 may be varied tocontrol the amount of drag resisting the tilting movement of the tiltdrum 44.

So that the sector assemblies 64 will be uniformly spaced from the dragdisk assembly 66 and so that the sector assemblies 64 will pivotsubstantially the same degree at substantially the same time, the sectorassemblies 64 are coupled together by way of drag links 80. The draglinks 80 are pivotally coupled to the drag sector assemblies 64 by dowelpins 82 which extend through holes 83 in the assemblies 64.

In accordance with one aspect of the invention, in order to control thespace between the sector assemblies 64 and the drag disk assembly 66,and consequently the resultant drag, the invention provides a linkagesystem which may be operated by a lever 50 or knob (not shown in FIGS. 2and 3), such as the tilt control lever 50 or the pan fluid drag knob 40.A drag link driver 84 is pivotally coupled to a sector assembly 131,which will be referred to as the driver sector assembly 64a, by a dragpin 86 assembled through the hole 88 in the driver sector assembly 64a.The opposite end of the drag link driver 86 is coupled to a crank arm 90by another dowel pin 92. The opposite end of the crank arm 90 is securedto the tilt control shaft 94, which is likewise secured to the lever 50(or knob 40). In this way, and as illustrated FIGS. 2 and 3, as anoperator rotates the lever 50 (or knob 40 to rotate worm gear 95a andgear 95b shown in dotted lines in FIG. 14) in the clockwise direction,the crank arm 90 and the drag link driver 84 operation to pivot thedriver sector assembly 64a away from the drag disk assembly 66, as shownin FIG. 3.

As the driver sector assembly 64a pivots, the dowel pins 82 and the endsof the drag links 80 rotate about the dowel pin 78. This rotation istranslated to the remaining sector assemblies 64 by the drag links 80 tocause the assemblies 64 to pivot on their respective dowel pins 78 anequal degree into or out of engagement with the drag disk 66. Thus, therotation of the lever 50 or knob 40 controls the distance between thedrag link sector assemblies 64 and the drag disk assembly 66 to controlthe drag force exerted on the rotating shaft 62.

In accordance with an important aspect of the invention, the drag system36, 48 operates with minimal slop or backlash. During operation ofconventional fluid drag systems, torque loads exerted on the dragcomponents during rapid panning and tilting may cause the components tochange their relative position. This movement may cause slop or backlashas the drag controls are adjusted. The invention provides a drag systemdesign 36, 48 in which the torque loads exerted on each sector assembly64 translate directly to the dowel pin 78 on which the assembly 64 ispivotally mounted to the housing 35. As a result, the torque exerted onthe sector assemblies 64 does not cause the assemblies 64 to adjusttheir relative position and move the lever 50 or knob 40. In this way,the drag assembly 36, 40 provides precise movement with minimal slop orbacklash.

Another important aspect of the invention, the counterbalance assembly56, will be described with reference to FIGS. 6 through 10. Thecounterbalance assembly is provided to counterbalance the torque exertedby the mounted instrument as it is tilted about the horizontal tilt axis42 and holds the instrument substantially steady when the instrument isreleased in a tilted position, as explained above.

As best shown in FIG. 6, the counterbalance assembly 56 mounted withinthe tilt drum 44 includes two pairs of springs 100 disposed in planeswhich are substantially perpendicular to the horizontal tilt axis 42 ofthe tilt drum 46. The ends of each pair of springs 100 are seated inrocker brackets 102, 103 journaled on a common axis 104, which isparallel to the horizontal tilt axis 42 and is disposed in asubstantially vertical plane 106 containing both axes 42, 104. Theopposite ends of the pairs of springs 100 are seated in rocker brackets108, 109 journaled at equal angles with respect to the vertical plane106 containing both axes 42, 104.

To provide a restoring torque as the tilt drum 44 rotates, the spacedrocker brackets 108, 110 rotate about the horizontal tilt axis 42. Therocker brackets 102, 103, while journaled to the axis 42, remaineffectively stationary. The restoring torque exerted by thecounterbalance spring system 56 substantially approximates the torqueexerted in the opposite direction by the increasingly tilted mountedcamera. As will be appreciated from the discussion which follows, themagnitude of the restoring force exerted is predictable and may beeasily adjusted to approximate the torque exerted by instruments havingvarious weights and centers of gravity by adjusting the length of thesprings 100 themselves, or the distance between the horizontal tilt axis42 and the common axis 104, which will be referred to as thecounterbalance radius 118.

Rotation of the counterbalance assembly 56 may best be understood byreferring to the schematic drawings of the counterbalance assembly 56shown in FIGS. 8 through 10. FIG. 8 shows the assembly 56 when theplatform 33 is at the level position. FIGS. 9 and 10 illustrate therelative positions of the springs 100 and rocker brackets 102, 103, 108,110 as the platform 33 and tilt drum 44 rotate 90° from level in theclockwise direction, and 90° from level in the counterclockwisedirection, respectively. As is evident from the figures, so long as thehorizontal tilt axis 42 and the common axis 104 do not coincide, or, inother words, so long as the counterbalance radius 118 is greater thanzero, the springs 100 will not maintain a constant length as theplatform 33 and tilt drum 44 rotate. As one spring set 100 lengthens,the other spring set 100 shortens during rotation. As a result of thislengthening and shortening of the springs 100, the counterbalanceassembly 56 exerts a restoring torque which varies linearly at low tiltangles, and follows a generally curve as the tilt angle increases, asillustrated by curves A through D in FIG. 11.

The panhead 30 may be used to support various types of equipment. Itwill be appreciated by one skilled in the art that the torque exerted bythe rotating mounted instrument is greater for a heavy instrument or aninstrument having a high center of gravity than a lighter instrument oran instrument having a lower center of gravity. Consequently, therestoring counterbalance torque required will vary according to theweight and center of gravity of the supported instrument. According toanother aspect of the invention, the counterbalance torque exerted bythe counterbalance assembly 56 may be adjusted in order to effectivelycounterbalance different instruments.

In order to adjust the level of restoring torque exerted by thecounterbalance assembly 56, the common axis 104, as defined by the crankpin 114, may be adjusted upward or downward within the crank pin supportassembly 116. It will be appreciated that the level of restoring torquewill vary as the counterbalance radius 118 is so adjusted. As the commonaxis 104 of the springs 100 approaches the tilt axis 42 about which therocker brackets 108, 110 are rotated, the changed length of the springs100 during rotation will decrease, and the restoring torque willlikewise decrease. Thus, the actual counterbalance torque mayeffectively be adjusted to zero by causing the common axis 104 tocoincide with the tilt axis 42.

As shown in FIG. 11, as the counterbalance radius 118 decreases, theresulting counterbalance torque will likewise decrease. Curves A-D showthe actual counterbalance torque for the counterbalance assembly 56 asthe distance of the counterbalance radius 118 decreases. Curve Arepresents the actual tilting platform 33 curve for a counterbalanceradius 118 of 0.431 inches. Curves B, C, and D show curves for radii of0.400, 0.250, and 0.100 inches, respectively.

According to an important aspect of the invention, the actualcounterbalance curves closely approximate the predicted theoreticaltorque exerted by the tilting platform 33 and an instrument supportedthereon. In this way, an operator may adjust the counterbalance assembly56 to attain the optimum restoring torque required to counterbalance therotation of the platform 33 and the supported instrument. Thetheoretical equation for the restoring torque required to counterbalancethe weight of the tilting platform 33 and instrument may be calculatedusing the following equation:

    restoring torque=W x sin α

where

W=combined weight of the platform 33 and the supported instrument

x=distance between the horizontal tilting axis 54 and the center ofgravity of the combined platform 33 and supported instrument

α=tilt angle of the platform 33 from horizontal

The theoretical torque curves for instrument and platform 33 havingvarious combinations of weights and centers of gravity are shown in FIG.11 as curves E through G. As shown in FIG. 11, the actual curves Athrough D closely approximate the theoretical curves represented bycurves E through G.

It will be appreciated that the configuration of the counterbalanceassembly may vary from that shown in the figures and described above.Two alternate embodiments of counterbalance spring systems areillustrated FIGS. 12 and 13. As shown in FIGS. 12 and 13, both thecommonly mounted ends 120, 122 and the angled ends 124, 126 of thesprings 128, 130 may be disposed above or below the tilt axis 132, 134.These embodiments, as well as the embodiment explained above, mayutilize either compression, extension, or torsion springs.

Referring now to FIG. 12, the rotating ends 124 of the springs 128 aremounted to a pivoted plate 135 at approximately the two o'clock and teno'clock positions. The opposite ends 120 of the springs 128 are fixed ata common mounting point. During operation, the plate 135, and hence thespaced ends 124 of the springs 128, rotate about the fixed tilt axis132. The distance between the common fixed ends 120 of the springs 128and the tilt axis 132, or the counterbalance radius 136 may be adjustedin order to affect a desired counterbalance torque curve.

In the embodiment shown in FIG. 13, one end of each spring 130 ismounted to pin 122 carried by rocker arm 137, a common point, while theopposite end 126 of each spring 130 is fixed at approximately the fouro'clock and eight o'clock positions. The commonly mounted ends of thesprings move as the rocker arm 137 rotates. By varying the length of therocker arm, the distance between the tilt axis 134 and the commonlymounted ends of the springs or counterbalance radius 138, may be variedin order to affect a desired counterbalance curve. The outboard ends 126of the springs 130 may also be adjusted outward to affect thecounterbalance torque curve.

Returning again to the embodiment shown in FIGS. 6 through 10, thecounterbalance assembly 56 will be described in more detail inreferences to FIGS. 6 and 7. The horizontal tilt axis 42 is defined bythe lock end tilt shaft 150 and the fluid end tilt shaft 152 disposed onopposite sides of the tilt drum 44. The tilt shafts 150, 152 arecastings which include generally circular plates 154, 156 with smallershaft extensions 158, 160 extending therefrom, respectively. The lockend and fluid end tilt shafts 150, 152 are journaled in the housing 35on the generally horizontal tilt axis 42 for rotation with respect tothe housing 35.

The counterbalance assembly 56 includes eight springs 100 disposed inpairs between lower whiffle trees 162, 164 and upper whiffle trees 166,168. The lower whiffle trees 162, 164 are rotatably supported along thecommon axis 104 defined by the crank pin 114. As will be apparent fromthe drawings, the crank pin axis 104 is parallel to and is disposed inthe vertical plane containing the horizontal tilt axis 42.

The upper whiffle trees 166, 168 are disposed in pairs, one pair 166being disposed on one side of the vertical plane 106, and the other pair168 being disposed on the opposite side of the plane 106. The upperwhiffle trees 166, 168 are rotatably coupled to whiffle tree supportshafts 170, 172 which are located at roughly the two o'clock and teno'clock positions, as shown in FIG. 6. The ends of the whiffle treesupport shafts 170, 172 are coupled to the lock end tilt shaft 150 atthe interface 174, and the fluid end tilt shaft 152 at the interface176. In this way, as the tilt drum 44 rotates about the horizontal axis42 defined by the lock end and fluid end tilt shafts 150, 152, theattached whiffle tree support shafts 170, 172 and rotatably supportedupper whiffle trees 166, 168 likewise rotate about the horizontal tiltaxis 42 of the tilt drum 44.

In order to maintain the relative spacing of the upper whiffle trees166, 168 along the support shafts 170, 172, cylindrical whiffle treespacers 178 are provided. The spacers 178 are disposed along the supportshafts 170, 172 between the upper whiffle trees 166, 168, and betweenthe upper whiffle trees 166 and the interfaces 174, 176 with the tiltshafts 150, 152, as shown in FIG. 7.

Referring again to FIG. 1, in order to adjust the level of restoringtorque exerted by the counterbalance assembly 56, a counterbalanceadjustment 58 is provided which controls the length of thecounterbalance radius 118, as explained above. As best illustrated inFIG. 14, to provide movement of the crank pin 114 within the verticalplane 106, the crank pin support assembly 116 includes a crank pin block184 slidably mounted in the counterbalance adjustment housing 186, whichis secured to the housing 35. To adjust the crank pin 114 up or down,the operator rotates the adjustment knob 58 to thread the crank pinadjustment screw 188, which extends through the adjustment housing 186,into or out of the block 184.

In order that the platform 33 may be held substantially steady at agiven tilt angle, the invention provides a locking mechanism within thelock end tilt assembly 51, which may be operated by the tilt lock lever54. As shown in FIG. 14, the locking mechanism includes a tilt lockscrew 190 which tightens against a tilt disk brake 192 to sandwich thebrake 192 between the tilt lock screw 190 and the tilt lock block 192 toprevent further tilting movement of the platform 33.

The tilt lock screw 190 and the tilt lock block 194 do not rotate aboutthe horizontal tilt axis 42 during tilting action of the tilt drum 44.The tilt lock block 194 is seated within openings in the main bodyhousing 35 and lock end cover 196. The tilt lock screw 190 is threadedinto an opening defined by the lock end cover 196 and the tilt lockblock 194. The tilt lock lever 54 is secured to the tilt lock screw 190by a screw 198. In this way, rotation of the tilt lock lever 54 resultsin axial movement of the attached tilt lock screw 190.

The tilt brake disk 192 is secured to the lock end tilt shaft 150 forrotation therewith by way of cap screws 200. Thus, as the tilt drum 44rotates about the horizontal tilt axis 42, the tilt brake disk 192rotates within the space defined by the tilt lock screw 190 and the tiltlock block 194. It will be appreciated that when the platform 33 is at adesired tilt angle, the operator can easily rotate the tilt lock lever54 to move the tilt lock screw 190 in an axial direction toward the tiltbrake disk 192 to sandwich the tilt brake disk 192 between the tilt lockscrew 190 and tilt lock block 194. In this way, the tilt brake disk 192,and consequently the platform 33 and tilt drum 44, may be locked atsubstantially any tilt angle within the tilting range.

The main body housing 35 may similarly be locked in any horizontalposition by the pan lock system shown in FIG. 15. The pan lock systemincludes a pan brake knob 42, a brake shaft 231, a pan brake insert 232,and a brake pad 233. The pan brake knob 42 is secured to the threadedbrake shaft 231 by a screw 234. So that the brake shaft 231 may berotationally assembled into the main body housing 35, an internallythreaded pan brake insert 232 is secured by a screw 235 within a cavityin the main body housing 35. In order to secure the main body housing 35against movement relative to the pan shaft 62, a brake pad 233 isdisposed in a horizontal opening adjacent the inward end of the brakeshaft 231 in the main body housing 35, as shown in FIG. 15. As isevident from the figure, rotation of the pan brake knob 42 andassociated brake shaft 231 results in an axial movement of the brakeshaft 231 within the main body housing 35. Axial movement of the brakeshaft 231 results in a corresponding axial movement of the abuttingbrake pad 233 within the main body housing 35. As the brake shaft 231 isrotated in toward the main body housing 35, the brake pad 233 is causedto bear against the surface of the pan shaft 62 to prevent movement ofthe main body housing 35 with respect to the pan shaft 62. As the brakeshaft 231 is rotated out from the main body housing 35, the brake pad233 is released from contact with the pan shaft 62, and the housing 35is free to rotate in a horizontal direction.

In summary, the invention provides a versatile panhead which willsmoothly and uniformly rotate 360° in the horizontal direction, and tilt90° up and 90° down. The counterbalance mechanism includes springs whichare disposed in a plane which is substantially vertical andperpendicular to the horizontal tilt axis of a tilt drum. The springsare disposed at an angle from a vertical plane that includes the tiltaxis, each having a mounting point along an axis defined by a crank pinwhich is parallel to the horizontal tilt axis. The crank pin is heldsteady while the opposite angled ends of the springs rotate about thetilt axis as the tilt drum rotates. The spring system exerts a restoringtorque which varies sinusoidally as the tilt angle increases toeffectively counterbalance the weight of a supported instrument as theinstrument rotates about the horizontal axis. The crank pin may be movedup or down to adjust the distance between the crank pin and tilt axis toaccount for instruments having different weights or centers of gravityand affect a desired counterbalance torque.

Tilting and panning movements are further controlled by tilt and pandrag systems. A drag disk assembly, comprising alternating sectors andsmaller sector spacers, are spaced about the disk assembly and pivotallymounted to the housing on dowel pins. The sector and disk assembliesvariably overlap to define a space therebetween in which a viscous fluidis interposed. The level of drag imposed by the drag system isdetermined by the size of the space between the disk and sectorassemblies, such that a minimum space results in maximum drag. The spacebetween the assemblies for both the tilt and drag systems may beadjusted by levers or knobs. Rotation of the lever or knob rotates anassociated crank arm to operate a drag link driver. The drag link driverdirectly pivots one of the sector assemblies toward or away from thedisk assembly. Drag links, which connect the sector assemblies, causethe remaining sector assemblies to pivot to an equal distance from thedisk assembly. In this way, the panhead may be easily and quicklyadjusted for smooth panning and tilting movements.

We claim as our invention:
 1. A panhead for supporting an instrumentcomprising, in combination,a housing, a tilt drum having a substantiallyhorizontal tilt shaft defining a horizontal tilt axis, means formounting said tilt drum in said housing for rotation about saidhorizontal tilt axis, a vertical pan shaft defining a vertical pan axis,means for mounting said housing on said vertical pan shaft for rotationabout said vertical pan axis, at least two springs mounted inperpendicular planes to said horizontal tilt axis, first means formounting one end of each of said springs along a common horizontal axis,said common axis lying in a vertical plane containing said tilt axis,second means for mounting the opposite end of each said spring at anequal angle to said vertical plane on opposite sides of said plane,means for securing against rotation relative to the tilt axis one end ofeach said spring having the same type means for mounting, means forcoupling the opposite ends of each said spring to said tilt drum forrotation therewith, such that said springs exert a restoring torque onthe tilt down when said tilt axis and said common axis do not coincide,at least one drag assembly for exerting a drag force against rotation ofone said shaft, said drag assembly including a circular drag diskassembly mounted to said shaft for rotation therewith, at least twosector assemblies pivotally mounted in said housing about thecircumference of said drag disk assembly so that said sector assembliespivot about axes which are parallel to said axis, said sector assembliesbeing mounted in said housing substantially adjacent to said drag diskassembly so as to define a space therebetween, each of said sectorassemblies being substantially equally distant from said disk assembly,means for pivoting one said sector assembly about its axis, means forcoupling said sector assemblies together so that pivoting one saidsector assembly causes each said sector assembly to pivot an equaldistance from said disk assembly, a viscous fluid disposed in said spacebetween said sector assemblies and said disk assembly whereby rotationof said shaft and said drag disk assembly exerts a drag force againstrotation.
 2. A panhead as claimed in claim 1 comprising two said dragassemblies, one being mounted along said horizontal tilt axis, the otherbeing mounted along said vertical pan axis.
 3. A panhead as claimed inclaim 1 wherein said means for coupling said sector assemblies togethercomprises at least two links and means for pivotally coupling the endsof said links to said sector assemblies such that pivoting one saidsector assembly causes the ends of said links coupled to said sectorassembly to rotate about said sector assembly pivot axis so that theopposite ends of said links coupled to another said sector assemblyexert a force on said other sector assembly to cause said other sectorassembly to rotate about its sector assembly pivot axis.
 4. A panhead asclaimed in claim 1, which further comprises means for varying thedistance between said common axis and said tilt axis.
 5. Acounterbalance mechanism for a panhead comprising, in combination,a tiltdrum mounted for rotation about a substantially horizontal tilt axis, atleast two springs mounted in perpendicular planes to said tilt axis,first means for mounting one end of each said spring along a commonhorizontal axis, said common axis lying in a vertical plane containingsaid tilt axis, second means for mounting the opposite end of each saidspring at an equal angle to said vertical plane on opposite sides ofsaid plane, means for securing against rotation relative to said tiltaxis one end of each said spring having the same type means formounting, means for coupling the opposite ends of each said spring tosaid tilt drum for rotation therewith, such that said springs exert arestoring torque on the tilt drum when said tilt axis and said commonaxis do not coincide.
 6. A counterbalance mechanism as claimed in claim5, which further comprises means for varying the distances between saidcommon axis and said tilt axis.
 7. A counterbalance mechanism as claimedin claim 6, wherein said second means for mounting the opposite end ofeach said spring at an angle is secured against rotation relative to thetilt axis.
 8. A counterbalance mechanism as claimed in claim 6, whereinsaid means for varying the distance includes a block and a housing, saidblock being coupled to said common axis, said block being slidablymounted along a vertical axis in said housing, whereby sliding saidblock in said housing causes said horizontal common axis to move withinsaid vertical plane.
 9. A counterbalance mechanism as claimed in claim8, wherein said means for varying the distance further includes anadjustment screw and an adjustment knob, said adjustment screw extendingthrough an opening in said housing and being threadably coupled to saidblock, whereby rotation of said adjustment knob causes said block toslide in said housing.
 10. A counterbalance mechanism as claimed inclaim 6, wherein said first means for mounting one end of each saidspring along a common horizontal axis is secured against rotationrelative to the tilt axis.
 11. A counterbalance mechanism as claimed inclaim 7, further comprising at least two support shafts and a crank pin,said crank pin lying along the common horizontal axis, each said springbeing mounted to said crank pin along the common horizontal axis, theopposite end of each said spring being mounted to said support shafts,said support shafts being coupled to said tilt drum for rotationtherewith.
 12. A counterbalance mechanism as claimed in claim 11 whereinsaid first and second means for mounting include whiffle trees which arerotatably mounted on said support shafts and said crank pin, said springends being mounted to said whiffle trees.
 13. A counterbalance mechanismas claimed in claim 12, wherein said springs are disposed in parallelpairs, the ends of each of said springs in said pairs being mounted tothe same whiffle trees.
 14. A counterbalance mechanism as claimed inclaim 13, having four pairs of springs, two pairs of said springs beingmounted at an angle to said vertical plane along one side of saidvertical plane and two pairs of said springs being mounted at an equalangle to said vertical plane along the other side of said verticalplane.
 15. A drag mechanism for a camera panhead comprising, incombination,a housing, a shaft mounted for rotation with respect to saidhousing about an axis of rotation, a circular drag disk assembly mountedto said shaft for rotation therewith, at least two sector assembliespivotally mounted in said housing so that said sector assemblies pivotabout axes which are parallel to said axis of rotation, said sectorassemblies being mounted in said housing about the circumference of saiddisk assembly substantially adjacent to said disk assembly so as todefine a space therebetween, means for variably pivoting one said sectorassembly about its axis, means for coupling said sector assembliestogether so that pivoting one said sector assembly causes each saidsector assembly to pivot to an equal distance from said disk assembly, aviscous fluid disposed in the space between the sector assemblies andthe disk assembly, whereby relative rotation of said shaft and saidcircular drag disk assembly with respect to said housing and said atleast two sector assemblies exerts a drag force against rotation.
 16. Adrag mechanism as claimed in claim 15, wherein said means for couplingsaid sector assemblies comprises at least two links and means forpivotally coupling the ends of said links to said sector assemblies suchthat pivoting one said sector assembly causes the ends of said linkscoupled to said sector assembly to rotate about said sector assemblypivot axis so that the opposite ends of said links coupled to anothersaid sector assembly exert a force on said other sector assembly tocause said other sector assembly to rotate about its sector assemblypivot axis.
 17. A drag mechanism as claimed in claim 16, wherein saidmeans for variably pivoting one said sector assembly comprises,a driverlink pivotally mounted to said one sector assembly, a crank armpivotally mounted to said driver link and to said housing, means forvariably pivoting said crank arm with respect to said housing, such thatpivoting said crank arm with respect to said housing exerts a force onsaid driver link which causes said one sector assembly to pivot aboutits axis to adjust the space between said sector assembly and said diskassembly.
 18. A drag mechanism as claimed in claim 17, wherein saidmeans for variably pivoting said crank arm with respect to said housingincludes a control shaft secured to said crank arm, and a lever securedto said control shaft.
 19. A drag mechanism as claimed in claim 17,wherein said means for variably pivoting said crank arm with respect tosaid housing includes a first control shaft secured to said crank arm, agear secured to said first control shaft, a second control shaftdisposed at an angle to said first control shaft, a worm gear secured tosaid second control shaft and disposed to mesh with said gear, and anadjustment knob secured to said second control shaft, such that rotationof said adjustment knob rotates said second control shaft and said wormgear, and rotation of said worm gear causes rotation of said gear andsaid first control shaft and pivoting of said crank arm.
 20. A dragmechanism as claimed in claim 16, wherein each said sector assemblyincludes at least one sector and at least one sector spacer, said sectorspacer being smaller in size than said sector, said sector and saidsector spacer being secured together to prevent relative motiontherebetween, and said drag disk assembly includes at least one dragdisk and at least one drag disk spacer, said sector assemblies beingmounted in said housing to define radial spaces between said sectors andsaid drag disk spacer, and between said sector spacers and said dragdisk.